This project continues to involve long-term observation of transplacentally carcinogen-exposed animals of the species Erythrocebus patas and Macaca fascicularis for tumor development, and concurrent short-term investigations of aspects of carcinogen metabolism, with biochemical parameters as an endpoint. Continuing studies on immunodeficiency virus-associated antigens are now reported in project ZOICPO5301. Preliminary characterization of the pleiotropic response of patas monkeys to hepatic enzyme induction by phenobarbital (PB) has been accomplished. This primate species was previously shown to be susceptible to promotion of hepatocellular carcinogenesis by PB. Initial experiments in PBtreated monkeys suggest the existence of a pleiotropic induction effect involving CYP2B and 3A, epoxide hydrolase, aldehyde dehydrogenase and other enzymes that in is comparable to the response previously characterized in rodents (see project Z01CPO5299).